Planetary power transmissions are used in both passenger vehicle and commercial vehicle applications. The powertrain in these vehicles generally includes an engine, a multi-speed transmission, and an output mechanism or differential.
The passenger vehicle of the past generally used a countershaft or synchronous-type transmission for providing the various speeds between the input and the output. Currently, both countershaft-type transmissions and planetary-type transmissions are employed in vehicle powertrains. In planetary-type transmissions, two or more planetary gearsets are controlled by a plurality of torque-transmitting mechanisms, commonly termed clutches and brakes to establish a plurality of speed ratios between a transmission input and a transmission output.
The planetary transmissions began as two-speed transmissions and developed into three-speed, four-speed, and five-speed type transmissions. Currently, there are a number of five-speed transmission units which are well known to the public, and also six-speed transmission units. One particular six-speed transmission is seen in U.S. Pat. No. 5,106,352 issued to Lepelletier on Apr. 21, 1992. The Lepelletier transmission incorporates an input gear mechanism or ratio-controlled set and an output planetary gearset, which provides a plurality of speed ratios. The Lepelletier concept employs five torque-transmitting mechanisms in the form of three rotating-type or clutches and two stationary-type or brakes.
It has become desirable more recently to incorporate six forward speed ratios in the planetary transmission thereby improving the overall performance and economy of the passenger vehicle.